The present invention relates to a cantilevered-roll stand. More particularly this invention concerns a support system for the shafts of such rolls.
In order to facilitate changing rolls and loading of a roll stand, it is known to cantilever the rolls. Thus, instead of mounting the rolls between the ends of a support shaft and supporting these end via appropriate bearings in a frame, the rolls are mounted at the ends of their shafts. Each shaft is supported in the frame on an outer bearing immediately adjacent the roll mounted on the one end of the shaft and an inner bearing at the other end of the shaft, and each shaft has between its bearings a gear that is operated by a drive unit.
German patent document 1,255,449 of Ohrnberger describes a system for pressurizing bearings of end-mounted rolls to compensate for rolling pressures. U.S. Pat. No. 4,036,030 of Papst describes a so-called pressure sleeve which hydraulically straightens a bent shaft in an end-mounted system, and U.S. Pat. No. 4,772,137 describes a similar oil-filled bearing/bushing which is used to correct deflections at the end of a shaft. Each of these systems works at the bearings where an end-mounted shaft for a center-mounted roll is carried in a frame.
The problem with the cantilevered systems is that, since each roll is only supported on one side, the outer bearing is greatly stressed and the shaft can bow somewhat. By making the frame and outer bearing extremely compact and rigid, it is possible to reduce vibration and deformation to a certain extent. Nonetheless in a finish rolling stand, it is still very difficult to reduce shaft deformation sufficiently to eliminate surface imperfections and variations in cross-sectional size in the workpiece being rolled.
It is therefore an object of the present invention to provide an improved cantilevered-roll support system.
Another object is the provision of such an improved cantilevered-roll support system which overcomes the above-given disadvantages, that is which allows even cantilevered rolls in a finish-rolling stand to be supported on axis without significant vibration or bowing of their support shaft.
A rolling stand has according to the invention a frame and a pair of support shafts centered on respective parallel shaft axes and each having an outer end projecting past the frame, inner and outer axially spaced bearing portions in the frame, and a gear between the respective inner and outer bearing portions. Each outer bearing portion lies between the respective inner bearing portion and the respective outer end. Respective rolls are carried on the outer ends outside the frame and respective eccentric sleeves rotatable in the frame about the axes engage the shafts at the bearing portions so that a spacing of the axes can be varied by rotating the sleeves in the frame. Respective pressure sleeves surround the shafts between the respective inner and outer bearing portions and are connected to a controller that pressurizes the sleeves and thereby bends the shafts in the frame between the inner and outer bearing portions.
These pressure sleeves, which can for example be formed substantially like a bearing and which set the play between the sleeve and the support shaft independently of their two bearings and independently of their oil feed, make it possible to act against bending of the support shafts and thus suppress spring-like oscillation movements of the rolls on the shafts. This improves the finish of the workpiece passing between the rolls and gives it a more uniform cross-sectional size. The shafts will not vibrate perceptibly.
The sleeves according to the invention are axially displaceable in the frame between the inner and outer bearing portions. Actuators can move them axially and/or angularly about the respective shaft axes to direct the radial forces from the sleeves against the shafts just where they are most needed to counter bending.
The sleeves are between the respective outer bearing portions and the respective gears. This places them just where bending is most pronounced.